Differential gene expression and the spatial distribution of differentially synthesized proteins within a cell lies at the core of the developmental process in both prokaryotes and eukaryotes. To ultimately define the regulatory circuitry which controls these processes, I believe it is essential to understand the structural and regulatory genes responsible for clearly defined morphogenetic events and to study the expression of these genes within the context of other cellular functions. The objectives of this research proposal are to understand the mechanisms by which the Caulobacter polar flagellum is assembled at a specific site on the cell and at a specific time in the cell cycle. To do this we will analyze the differentially synthesized protein components of the flagellum and initiate a program to study the differentially expressed chemotaxis sensory transduction system which controls flagellar rotation. A selected sample of the multiple genes involved in flagellum biogenesis and function will be isolated, mapped, and analyzed with particular attention to genomic arrangement and the function of regulatory sequences. Those, and flagellar regulatory and structural genes already isolated, will be used to determine the steps in the Caulobacter differentiation process which are controlled at the transcriptional and/or post-transcriptional level.